Abstract

Objective: Low monoamine oxidase (MAO) activity and the neurotransmitter dopamine are 2 important factors in the development of alcohol dependence. MAO is an important enzyme associated with the metabolism of biogenic amines. Therefore, the present study investigates whether the association between the dopamine D2 receptor (DRD2) gene and alcoholism is affected by different polymorphisms of the MAO type A (MAOA) gene.Methods: A total of 427 Han Chinese men in Taiwan (201 control subjects and 226 with alcoholism) were recruited for the study. Of the subjects with alcoholism, 108 had pure alcohol dependence (ALC) and 118 had both alcohol dependence and anxiety, depression or both (ANX/DEP ALC). All subjects were assessed with the Chinese Version of the Modified Schedule of Affective Disorders and Schizophrenia-Lifetime. Alcohol dependence, anxiety and major depressive disorders were diagnosed according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria.Conclusion: The genetic variant of the DRD2 gene was only associated with the ANX/DEP ALC phenotype, and the genetic variant of the MAOA gene was associated with pure ALC. Subjects carrying the MAOA 3-repeat allele and genotype A1/A1 of the DRD2 were 3.48 times (95% confidence interval = 1.47-8.25) more likely to be ANX/DEP ALC than the subjects carrying the MAOA 3-repeat allele and DRD2 A2/A2 genotype. The MAOA gene may modify the association between the DRD2 gene and ANX/DEP ALC phenotype.

Acknowledgements: This study was supported in part by National Science Council Grants NSC 92-2314-B-006-151, NSC93-2314-B-006-108, NSC94-2314-B-006-116, NSC94-2314-B-016-016 and NSC95-2314-B-016-019; the Department of Health Grants DOH 88-TD-1107 and DOH94-TD-D-113-040; Tri-Service General Hospital Grant TSGH-C94-76, and by National Cheng Kung University Project of Promoting Academic Excellence and Developing World Class Research Centers, Taiwan, Republic of China. Thanks to Mr. Cheng-Chang Huang, A-Lan Tang and Fu-Kuei Chang for their assistance in preparing this manuscript.

Contributors: Drs. Huang, Lin, Ko, and Lu, Ms. Chang and Ms. Wu designed the study. Drs. Huang, Wan, Wang and Lu, Ms. Chang and Ms. Wu aquired the data, which Drs. Huang, Lin, and Lu, and Ms. Wu analyzed. Drs. Huang and Lu wrote the article, and all authors revised it. All authors gave final approval for the article to be published.